Active Control of Graphene-Based Unidirectional Surface Plasmon Launcher

The manipulation of surface plasmon polariton (SPP) propagation is a basic subject for the realization of novel optical devices. Although the unidirectional SPP launcher has been demonstrated, it has been difficult to realize active control suitable for device applications. Here, we propose a graphene device with electrically controllable propagation of SPPs. The source/drain electrode of this device is made of a reflective antenna pair structure, with its optical resonance controlled by the corresponding applied voltage. With appropriate source and drain bias, this device can serve as a good unidirectional SPP launcher, with a high extinction ratio over 2000 and generation efficiency of 0.38. The electrical control allows us to tune the propagation of SPPs with significant flexibility, which may be used for future novel plasmonic devices and photonic circuits.